The monocyte is an important cell in the pathogenesis of AIDS. New models of HIV-1 "latency" in monocytes are needed to address questions regarding factors which predispose patients to progression to AIDS and possible therapeutic interventions. These investigations will develop a new model of monocyte "latency" and study induction of HIV-1 replication by two physiologic "activating factors," 1,25(OH)2cholecalciferol (1,25(OH)2D3) and cytomegalovirus (CMV). This will be accomplished as follows: 1) Both monocyte-tropic and lymphocyte-tropic strains of HIV-1 will be used to infect A3.5 cells (a monocytoid cell line) and peripheral blood monocytes separated by elutriation. A panel of acutely-infected, chronically-infected, and cloned A3.5 cells will be generated. HIV-1 DNA, RNA, and protein expression in these cells will be analyzed. 2) Cells and clones which produce little or no HIV-1 RNA or proteins (but harbor HIV-1 proviral DNA - i.e. "latency-infected" monocytes) will be "activated" with 1,25(OH)2D3 or CMV. Alterations in HIV-1 DNA, RNA, and protein expression will be analyzed to determine the level of regulation by these factors. 3) The cellular regulatory proteins and the corresponding DNA binding regions which are important in mediating activation of HIV-1 replication by 1,25(OH)2D3 and CMV at the transcriptional level will be determined. These investigations may suggest possible therapeutic interventions to block activation of HIV-1 thus extend the period of clinically asymptomatic infection.